JP4663257B2 - Light emitting device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a display device including a light-emitting element and a manufacturing method thereof.

  In recent years, in a display device having a light-emitting element or a liquid crystal element, the screen is increased in size and definition, and the number of wirings such as signal lines and scanning lines and the length of the wirings tend to increase. Therefore, it is necessary to prevent a voltage drop due to wiring resistance and to prevent a signal writing failure or a gradation failure.

Thus, there is a configuration in which an auxiliary wiring made of a transparent conductive film is connected to a transparent electrode of a light emitting element through an anisotropic conductor (see Patent Document 1). According to Patent Document 1, since the effective resistance value of the transparent electrode can be lowered and a uniform voltage can be applied to the light emitting element, display defects such as display unevenness can be prevented. Are listed.
JP 2002-33198 A

  The present invention provides a display device capable of lowering the effective resistance value of electrodes such as transparent electrodes and wiring and applying a uniform voltage to the light emitting elements by a method different from that of Patent Document 1. Is an issue.

  A light-emitting element included in the display device includes a first electrode and a second electrode in order to apply a voltage to the light-emitting layer. Since the second electrode can be shared by each light emitting element, that is, each pixel, the second electrode can be formed on the light emitting layer without patterning. Such a second electrode needs to apply a uniform voltage to the light emitting layer.

  In addition, in the case where light from the light emitting layer is emitted to the opposite side to a substrate provided with a semiconductor element typified by TFT (hereinafter referred to as top emission), the second electrode needs to have translucency. . Therefore, the second electrode has a transparent conductive film, for example, an ITO (indium tin oxide). However, the resistance value of the transparent conductive film was high. The second electrode may be a thin metal film, but its resistance value is high due to its thinness. As a result, there is a concern that the power consumption of the display device may be hindered.

  In particular, as the display device becomes larger, it is important to apply a uniform voltage to the light emitting layer. However, as described above, it is difficult to apply a uniform voltage because the resistance of the second electrode is high. Furthermore, there is a concern that the power consumption of the display device increases.

  In view of the above, an object of the present invention is to provide a display device having a new configuration capable of reducing the substantial resistance value of the second electrode and applying a uniform voltage to the light emitting element.

  In view of the above problems, the present invention is characterized in that a conductive film (hereinafter referred to as auxiliary wiring) is connected to an electrode or a wiring represented by the second electrode.

The auxiliary wiring is preferably formed in the conductive film so as to include a low-resistance material, and particularly preferably formed so as to include a material lower than the resistance of the electrode or wiring that needs to be lowered. Specifically, an element selected from Ta, W, Ti, Mo, Al, and Cu, an alloy material or compound material containing the element as a main component, or a transparent conductive film such as ITO or SnO ₂ is formed. can do. Further, even when ITO having a high resistance value is used as the auxiliary wiring, the substantial resistance value of the second electrode can be lowered by providing the auxiliary wiring.

  The above auxiliary wiring can be formed by a sputtering method, a plasma CVD method, a vapor deposition method, a printing method, or a spin coating method. The auxiliary wiring may have a predetermined shape using a mask, and may further be etched to have a predetermined shape by dry etching or wet etching.

  In particular, the present invention differs from Patent Document 1 in which an auxiliary wiring connected to a transparent electrode is newly formed, and is the same layer (same layer) as a conductive film such as an electrode or wiring of a semiconductor element, a signal line, a scanning line, or a power supply line. Auxiliary wiring is formed on the substrate. Alternatively, an auxiliary wiring is formed over an insulating film provided with a conductive film such as an electrode or wiring of a semiconductor element, a signal line, a scanning line, or a power supply line. More preferably, the auxiliary wiring is formed using the same material as the conductive film such as an electrode or wiring of a semiconductor element, a signal line, a scanning line, or a power supply line. As a result, it is not necessary to provide a process for auxiliary wiring, and a mask for auxiliary wiring is not increased.

  Semiconductor elements include thin film transistors (TFTs) using non-single crystal semiconductor films typified by amorphous silicon and polycrystalline silicon, MOS transistors formed using semiconductor substrates and SOI substrates, junction transistors, and organic semiconductors. Alternatively, a transistor using carbon nanotubes or other transistors can be used.

  For example, when a TFT is used as the semiconductor element, the TFT includes at least a first insulating film provided so as to cover a gate electrode provided over the semiconductor film, and a second insulating film provided over the first insulating film. As the insulating film is stacked, the area where the auxiliary wiring is provided can be increased, and the resistance can be further reduced.

  The first insulating film and the second insulating film include an inorganic material containing silicon such as silicon oxide, silicon nitride, or silicon nitride oxide, or polyimide, polyamide, acrylic, BCB (benzocyclobutene), or a resist. It can be formed from organic materials. Further, in order to achieve planarization, the first insulating film, the second insulating film, and the like may be polished by physical means such as a CMP (Chemical Mechanical Polishing) method.

  An auxiliary wiring may be used for a wiring to be connected to an external circuit (hereinafter referred to as a wiring). Since the lead wiring is provided along the outer periphery of the panel up to the connection portion with the external circuit, it is preferable to form the lead wiring with an auxiliary wiring having a lower resistance.

  The present invention is not limited to the configuration in which the auxiliary wiring is connected to the second electrode (transparent conductive film) as long as the auxiliary wiring is connected to the wiring that requires low resistance.

  The present invention is not limited to providing an auxiliary wiring for a display device having a light-emitting element, and an auxiliary wiring may be provided for a display layer having a liquid crystal element to reduce the resistance of electrodes and wiring. .

  With the auxiliary wiring of the present invention, the substantial resistance value of an electrode or wiring represented by the second electrode can be lowered. The substantial resistance value refers to the combined resistance of electrodes and wiring. As a result, reduction in power consumption in the display device and prevention of voltage drop due to electrodes and wiring can be achieved.

  In addition, signal writing failure and gradation failure due to wiring resistance can be prevented. Further, in the case of the second electrode, by connecting to the auxiliary wiring, the occurrence of a voltage drop can be suppressed and a uniform predetermined voltage can be applied to the light emitting element. As a result, display quality can be improved.

  In particular, in a large display device, the effect of lowering the substantial resistance value of electrodes and wirings is remarkable.

By connecting the auxiliary wiring to the electrode or wiring in the display device, the substantial resistance value can be reduced. As a result, power consumption in the display device can be reduced.

  In addition, signal writing failure and gradation failure due to wiring resistance can be prevented. Further, the occurrence of a voltage drop is suppressed, and a uniform predetermined voltage can be applied to the light emitting element. As a result, display quality can be improved.

  In particular, in a large display device, the effect of lowering the substantial resistance value of electrodes and wirings is remarkable.

  Embodiments of the present invention will be described below with reference to the drawings. However, the present invention can be implemented in many different modes, and those skilled in the art can easily understand that the modes and details can be variously changed without departing from the spirit and scope of the present invention. Is done. Therefore, the present invention is not construed as being limited to the description of this embodiment mode. Note that in all the drawings for describing the embodiments, the same portions or portions having similar functions are denoted by the same reference numerals, and repetitive description thereof is omitted.

(Embodiment 1)
In this embodiment mode, a structure of a pixel portion of a display device having an auxiliary wiring is described.

  In FIG. 1, a p-channel TFT (polycrystalline TFT) using polycrystalline silicon as an example of a semiconductor element, a transparent conductive film as an example of a second electrode, and a transparent conductive film as a second electrode are employed. Shows the configuration of the pixel portion of the display device connected to the auxiliary wiring.

  FIG. 1A illustrates a structure in which the second electrode is connected to the auxiliary wiring, and the auxiliary wiring is formed in the same layer as the first electrode. Note that the auxiliary wiring may be formed from the same material as the first electrode or from a different material.

  The pixel portion of the display device includes a base insulating film 11, a semiconductor film 12, a gate insulating film 14, a gate electrode 15, a protective film 23, and first to third insulating films 16 to 18 which are sequentially formed on the insulating surface 10. The first electrode 19, the light emitting layer 20, and the second electrode 21 for applying a voltage to the light emitting layer are included, and the auxiliary wiring 25 is provided in the same layer as the first electrode 19.

  An amorphous semiconductor film such as an amorphous silicon film is formed on the base insulating film 11. The amorphous semiconductor film is patterned into a predetermined shape to form an island-shaped semiconductor film 12. The base insulating film 11 may have a structure in which insulating films containing silicon are stacked, for example, a structure in which insulating films such as a silicon oxide film, a silicon nitride film, or a silicon oxynitride film are stacked.

  The semiconductor film 12 is crystallized by laser or heating. A gate electrode 15 is formed over the crystallized semiconductor film (crystalline semiconductor film). The gate electrode 15 may have a structure in which a conductive film is stacked, for example, a structure in which a W film is stacked on a TaN film. Impurity region 13 is formed in a self-aligning manner using gate electrode 15 as a mask. The first insulating film 16 includes, for example, an inorganic material, and is formed so as to cover the gate electrode and the semiconductor film.

  Thereafter, the semiconductor film may be recrystallized by heating in a state where the protective film 23 is formed so as to cover the gate electrode 15. In particular, when the protective film 23 is formed by the CVD method, the source gas may be controlled so as to contain a large amount of hydrogen.

  A wiring (source wiring or drain wiring) 22 connected to the impurity region 13 is formed through a contact hole (opening) provided in the first insulating film 16. In addition, signal lines, power supply lines, and the like are formed in the same layer as the wiring. The second insulating film 17 includes, for example, an inorganic material, and is formed so as to cover the wiring, the signal line, the power supply line, and the like.

  A first electrode 19 is formed so as to be connected to the wiring 22 through a contact hole provided in the second insulating film 17. At this time, the auxiliary wiring 25 is formed in the same layer. The auxiliary wiring 25 may be formed using the materials described above. A third insulating film 18 corresponding to a bank is formed so as to cover the first electrode 19 and the auxiliary wiring 25. The third insulating film 18 is formed so as to have an inorganic material, for example. A light emitting layer 20 is formed on the first electrode 19 through a first contact hole provided in the third insulating film 18.

  The light emitting layer for each color of RGB may be formed separately to form a full color display, or the light emitting layer for white light emission may be formed as a whole. When a white light emitting layer is used, full color display may be performed by using a color filter or a color conversion layer on the counter substrate side. In the case of performing monochromatic display, area color display in which a light emitting layer of a predetermined color is formed may be used.

  Then, the second electrode 21 is formed so as to cover the light emitting layer 20. At this time, a second contact hole is provided in the third insulating film 18 above the auxiliary wiring 25 at the same time, and the second electrode 21 and the auxiliary wiring 25 are connected through the second contact hole. . The second contact hole can be formed in a line shape, a dot shape, or a combination thereof.

  The first electrode 19 and the second electrode 21 can be an anode or a cathode based on the light emission direction and the polarity of the semiconductor element. In this embodiment mode, a case where the first electrode is an anode, the second electrode is a cathode, and light is emitted to the second electrode side will be described.

  In this case, it is preferable to use a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a high work function (work function of 4.0 eV or more) as the anode material. Specific examples of the anode material include ITO (indium tin oxide), indium oxide mixed with 2 to 20% zinc oxide (ZnO), IZO (indium zinc oxide), gold (Au), platinum (Pt), Nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), or metal nitride (TiN), etc. Can be used.

On the other hand, as the cathode material, it is preferable to use a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a low work function (work function of 3.8 eV or less). Specific examples of the cathode material include elements belonging to Group 1 or Group 2 of the element periodic rule, that is, alkali metals such as Li and Cs, and alkaline earth metals such as Mg, Ca, and Sr, and alloys containing these (Mg : Ag, Al: Li) and compounds (LiF, CsF, CaF ₂ ), as well as transition metals including rare earth metals. However, since the cathode needs to have a light-transmitting property, these metals or alloys containing these metals are formed very thinly and laminated with a transparent conductive film such as ITO.

  These anode and cathode can be formed by vapor deposition, sputtering, or the like.

  On the second electrode, a passivation film 29 having an insulating film mainly composed of silicon nitride or silicon nitride oxide obtained by sputtering (DC method or RF method) or a DLC film (Diamond Like Carbon) containing hydrogen. Form.

In this manner, the pixel portion of the display device can be formed.

  FIG. 1B shows a structure of a pixel portion of a display device in which an auxiliary wiring 25 is provided over the second insulating film 17 and a fourth insulating film is provided, unlike FIG. 1A. The other structures are the same as those in FIG.

  A second insulating film 17 is formed so as to cover the wiring 22, and a contact hole is formed. An auxiliary wiring 25 is provided on the second insulating film 17, and the auxiliary wiring 25 is also formed in the contact hole. A third insulating film 18 is formed so as to cover the auxiliary wiring 25, and a contact hole is formed. A first electrode 19 is formed on the third insulating film and in the contact hole, and the wiring 22 and the first electrode 19 are connected through the auxiliary wiring 25. Further, a fourth insulating film 26 corresponding to a bank is formed so as to cover the first electrode 19.

  A light emitting layer 20 is formed on the first electrode 19, and a second electrode 21 is formed so as to cover the light emitting layer 20. At this time, the second electrode 21 is connected to the auxiliary wiring 25 through contact holes formed in the second insulating film 17 and the third insulating film 18.

  The stack structure of the first to third insulating films is not limited to that shown in FIG. 1B, and an insulating film may be further stacked. A structure in which insulating films are stacked as in FIG. 1B is preferable because there are few layout restrictions for forming electrodes, wirings, and the like. In particular, since there is little restriction on the area where the light emitting layer is provided, the area of the light emitting region can be increased. Furthermore, since there is little restriction on the area where the auxiliary wiring is provided, the auxiliary wiring can be formed in a larger area. As a result, lower resistance electrodes and wiring can be provided, and power consumption can be reduced.

  As described above, the structure in which the insulating film includes the inorganic material has been described, but an organic material can also be used for the insulating film. Organic materials have higher flatness than inorganic materials. In some cases, etching for forming a contact hole can be eliminated. As a result, it is possible to reduce processes and waste. Note that an organic material such as acrylic or polyimide has a hygroscopic problem, and thus a protective film such as a SiN film is preferably provided. In addition, since the resist has a lower hygroscopicity than an organic material such as acrylic or polyimide, a resist film such as a SiN film is unnecessary and is preferable. Furthermore, the cost is lower than that of acrylic or polyimide, and the diameter of the contact hole formed by exposure is preferably small. However, a resist is often colored, and thus is preferably used for a bottom emission display device that emits light from a substrate provided with a semiconductor element typified by a TFT.

  Hereinafter, the case where an insulating film is formed using a resist as an organic material will be described with reference to FIG. The other structures are the same as those in FIG.

  First, as in FIG. 1A, the wiring 22 is formed, and the auxiliary wiring 25 is formed at the same time. The auxiliary wiring 25 may be formed from the same material as the wiring 22 or from a different material.

  Thereafter, in FIG. 1C, as a positive resist, a solution obtained by dissolving cresol resin or the like in a solvent (propylene glycol monomethyl ether acetate; PGMEA) is applied by a spin coating method. After the resist is applied, the resist is heated and baked at 80 to 150 degrees using a superheater (oven, hot plate) or the like (this is referred to as pre-baking).

  After baking, a mask pattern is formed so that a predetermined contact hole is formed in the second insulating film 17 and exposed. Then, the mask pattern is transferred to the resist. Since a positive resist material is used in this embodiment mode, a contact hole is formed at a position where light is irradiated. Thereafter, when the developer is dropped or sprayed, the resist in the portion exposed to light is melted, and a predetermined contact hole is formed in the second insulating film 17. When a negative resist material is used instead of the positive resist material, the resist at the position where light did not appear is dissolved in the developer, and a contact hole is formed.

  In the case where an insulating film is formed using an organic material, when the predetermined thickness is not reached, it is preferable to apply the solution repeatedly or repeat pre-baking and application.

  After the contact holes are formed, heat treatment is performed at 120 to 250 degrees using a superheater (oven, hot plate) or the like in order to remove moisture remaining in the resist and at the same time make it more stable. Bake).

  Of the plurality of contact holes formed in the second insulating film 17, the first electrode 19 is formed in the first contact hole and connected to the wiring 22. The auxiliary wiring 25 is exposed in the second contact hole of the second insulating film 17. That is, the second contact hole is formed so that the side surface of the auxiliary wiring 25 is not in contact with the end portion of the second insulating film 17. The auxiliary wiring 25 may be formed after forming the second insulating film 17.

  A third insulating film 18 corresponding to a bank is formed using the same resist material and method as those for the second insulating film 17. A contact hole of the third insulating film 18 is formed so that the entire auxiliary wiring 25 is exposed. That is, a contact hole having a diameter such that the side surface of the auxiliary wiring 25 is not in contact with the end portion of the third insulating film 18 is formed.

  A light emitting layer 20 is formed so as to cover the third insulating film 18. At this time, on the side surface of the auxiliary wiring 25, the light emitting layer 20 is thin, so that it is cut off. That is, the light emitting layer 20 is formed excluding a part of the surface of the auxiliary wiring 25, specifically, a part of the side surface of the auxiliary wiring 25.

  A second electrode 21 is formed so as to cover the light emitting layer 20. Since the second electrode 21 is formed so as to be formed up to the side surface of the auxiliary wiring 25, electrical connection can be established. For example, when the second electrode 21 is formed by thinly forming a metal film containing an element belonging to Group 1 or Group 2 of the element periodic rule and laminating a transparent conductive film on the metal film, the metal film or the transparent conductive film is formed. It is only necessary that the film is electrically connected to the auxiliary wiring 25.

  That is, in the structure illustrated in FIG. 1C, it is possible to eliminate the need for forming a contact hole for electrically connecting the auxiliary wiring 25 and the second electrode 21.

  In the structure illustrated in FIG. 1C, an organic material may be further used for the first insulating film 16. A plurality of insulating films are preferably formed using the same material because the manufacturing process is simplified.

  1A and 1B, a contact hole is formed so that an insulating film is not provided at the end of the auxiliary wiring 25, and the light emitting layer 20 is formed over the entire pixel region. The light emitting layer 20 can be formed on the auxiliary wiring 25 so as to be interrupted.

  As shown in FIGS. 1A to 1C, the substantial resistance value of the second electrode 21 can be reduced by providing the auxiliary wiring 25. As a result, power consumption in the display device can be reduced.

  In addition, signal writing failure and gradation failure due to wiring resistance can be prevented. Further, in the case of the second electrode 21, by connecting to the auxiliary wiring 25, the occurrence of a voltage drop can be suppressed and a uniform predetermined voltage can be applied to the light emitting element. As a result, display quality can be improved.

  In particular, in a large display device, the effect of lowering the substantial resistance value of electrodes and wirings is remarkable.

  Note that the layer where the auxiliary wiring is provided is not limited to the structure shown in this embodiment mode. For example, the auxiliary wiring may be provided in the same layer as the gate electrode. A plurality of auxiliary wirings formed in a plurality of layers may be connected through contact holes.

  The structure of the TFT shown in this embodiment mode is not limited, and a structure having a low concentration impurity region, a structure in which the impurity region or the low concentration impurity region overlaps with the gate electrode, or a plurality of gate electrodes are provided for the semiconductor film Alternatively, a structure in which gate electrodes are provided above and below the semiconductor film, or the like can be used.

  In this embodiment mode, a substrate on which a semiconductor element typified by a TFT is provided, a top emission display device that emits light from a light emitting layer on the opposite side, a bottom emission display device, and light is emitted on both sides. The present invention can be applied to a dual emission type display device that emits light.

(Embodiment 2)
In this embodiment mode, description will be made on the entire display device, in particular, routing wiring for connection to an external circuit. In particular, a routing wiring (hereinafter referred to as an anode line) having the same potential as the high potential voltage VDD and a routing wiring (hereinafter referred to as a cathode line) having the same potential as the low potential voltage VSS will be described with reference to FIG. Note that FIG. 2 illustrates only wirings arranged in the column direction in the pixel portion 104.

FIG. 2A shows a top view of the panel. A pixel portion 104 in which a plurality of pixels 105 are arranged in a matrix on a substrate 100, a signal line driver circuit 101 around the pixel portion 104, and scanning Line drive circuits 102 and 103 are arranged. The number of these driver circuits is not limited to that shown in FIG. 2A, and a plurality of signal line driver circuits or a single scan line driver circuit may be arranged depending on the structure of the pixel 105.

The signal lines 111 arranged in the column direction in the pixel portion 104 are connected to the signal line driver circuit 101. The power supply lines 112 to 114 arranged in the column direction are connected to any one of the anode lines 107 to 109. The auxiliary wiring 110 arranged in the column direction is connected to the cathode line 106. The anode lines 107 to 109 and the cathode line 106 are routed so as to surround the pixel circuit 104 and a drive circuit disposed in the periphery thereof, and are connected to an external circuit (FPC: Flexible printed circuit). Connected to the terminal.

The anode lines 107 to 109 are preferably formed corresponding to any of RGB colors. This is because variation in luminance occurring between the colors can be corrected by changing the potential of the anode lines 107 to 109. That is, since the current density of the electroluminescent layer of the light emitting element is different for each color, it is possible to improve the problem that the luminance differs for each color even when the same current value is passed.

In this embodiment, it is assumed that the RGB light-emitting layers are separately applied. However, there is a problem in the difference in current density in each color, such as a method of using a light-emitting layer that emits white light and a color filter as a colorization method. In the case of adopting a method that does not, there is no need to provide a plurality of anode wires.

FIG. 2B shows a mask layout diagram. The anode lines 107 to 109 and the cathode line 106 are arranged around the signal line driver circuit 101, and the anode lines 107 to 109 are arranged in the column in the pixel portion 104. The power supply lines 112 to 114 arranged in the direction are connected through contact holes.

In this embodiment, the cathode line 106 and the anode lines 107 to 109 are formed of a conductive film in the same layer as the auxiliary wiring 110. Since the auxiliary wiring is formed of a material having a lower resistance, it is preferable that the cathode line and the anode line drawn so as to surround the drive circuit be a conductive film in the same layer.

After forming the cathode line 106, the anode lines 107 to 109, and the auxiliary wiring 110, the first electrode of the light emitting element is formed, and an insulating film corresponding to the bank is formed. A contact hole is formed in the insulating film located above the region where the cathode line 106 is formed, the region where the light emitting layer is formed, and the region where the auxiliary wiring is formed. By forming the contact hole, the cathode line 106, the first electrode, and the auxiliary wiring 110 are exposed. As shown in FIGS. 1A to 1C, a light emitting layer is formed in the contact hole on the first electrode. At this time, each RGB light emitting layer may be separately deposited with a metal mask and evaporated, and a white light emitting layer may be evaporated on the whole.

Next, a second electrode covering the light emitting layer is formed. At this time, the second electrode formed on the light emitting layer is connected not only to the cathode line 106 but also to the auxiliary wiring 110 arranged in the column direction in the pixel portion 104. By the configuration in which the second electrode and the auxiliary wiring are connected in the pixel portion, the substantial resistance value of the second electrode can be reduced. Therefore, it is possible to improve image quality defects and power consumption problems due to the resistance of the second electrode.

Note that the layer for forming the auxiliary wiring 110 is not limited to a conductive film in the same layer as the signal line as illustrated in FIG. 2B, and a conductive film in the same layer as the scanning line may be used. The shape of the contact hole between the auxiliary wiring 110 and the second electrode is not limited to that shown in FIG. 2B, and the contact hole may be provided in a line shape in the column direction or may be provided in a dot shape. Further, it may be provided in a line shape in the row direction, or may be provided in a dot shape. Hereinafter, the layout of contact holes between the auxiliary wiring 110 and the second electrode will be described with reference to FIGS. 3 to 6 show the signal line 111, the auxiliary wiring 110, the cathode line 106, and the scanning line 120 in the pixel portion 104.

In FIG. 3, a contact region 121 between the auxiliary wiring 110 and the cathode line 106 is formed, and the auxiliary wiring 110 and the second electrode in each pixel 105 are connected via a circular (dot-shaped) contact hole 122. ing.

  In FIG. 4, a contact region 121 between the auxiliary wiring 110 and the cathode line 106 is formed, and the auxiliary wiring 110 and the second electrode in each pixel 105 are connected via a linear (line-shaped) contact hole 122. ing. That is, the contact region 121 and the linear contact hole 122 are simultaneously formed and connected.

  The contact hole 122 shown in FIG. 4 is formed larger than the auxiliary wiring 110. In the structure shown in FIG. 1C, the contact hole 122 is larger than the auxiliary wiring 110, and in the structure shown in FIGS. 1A and 1B, the contact hole 122 is smaller than the auxiliary wiring 110.

  In FIG. 5, a contact region 121 between the auxiliary wiring 110 and the cathode line 106 is formed, and two auxiliary wirings 110 are provided in each pixel 105. The auxiliary wiring 110 and the second electrode are circular (dots). Are connected via a contact hole 122. Circular contact holes 122 are formed at the four corners of each pixel.

  Thus, a plurality of auxiliary wirings 110 may be provided for each pixel. Further, a plurality of auxiliary wirings may be provided in a stacked manner.

  In FIG. 6, the auxiliary wiring 110 is formed in the same layer as the gate wiring, the contact region 121 between the auxiliary wiring 110 and the cathode line 106 is formed, and the auxiliary wiring 110 and the second electrode in each pixel 105 are connected. They are connected via contact holes 122 having a certain area (area shape).

  As shown in FIGS. 3 to 6, the layout of contact holes between the auxiliary wiring 110 and the second electrode can be various. Any of the configurations shown in FIGS. 3 to 6 can be combined as the shape of the contact hole such as a circle, a line, or an area.

  Note that when the auxiliary wiring 110 and the second electrode are sufficiently connected via the contact hole 122 in the pixel portion, the contact region 121 with the cathode line 106 and the cathode line 106 under the contact region 121 are not necessary. be able to. In this case, it is preferable to use the same layer as the auxiliary wiring, the gate wiring, or the source / drain wiring as the routing wiring for connecting the second electrode to the FPC.

(Embodiment 3)
In this embodiment, an equivalent circuit of a pixel portion of a display device is described.

A pixel circuit illustrated in FIG. 7A includes a light-emitting element 39, a signal line 30 to which a video signal is input, and a transistor (switching transistor) used as a switching element for controlling input of the video signal to the pixel. 35, a transistor (drive transistor) 36 for controlling the value of the current flowing to the light emitting element 39, a transistor (current control transistor) 37 for controlling the supply of current to the light emitting element 39, and a second of the light emitting element 39 Auxiliary wiring 34 connected to the electrodes. Further, as in this embodiment, a capacitor 38 for holding the potential of the video signal may be provided.

The driving transistor 36 and the current control transistor 37 are preferably formed to have the same polarity. In this embodiment mode, the case of a p-channel type is described.

In the present embodiment, the driving transistor 36 is operated in the saturation region and the current control transistor 37 is operated in the linear region. Therefore, the channel length L of the driving transistor 36 may be longer than the channel width W, and L of the current control transistor 37 may be the same as or shorter than W. More preferably, the ratio of L to W of the driving transistor 36 is 5 or more.

The driving transistor 36 may be an enhancement type transistor or a depletion type transistor. In this embodiment, the case where a depletion type transistor is used will be described.

The gate of the switching transistor 35 is connected to the scanning line 31. One of the source and the drain of the switching transistor 35 is connected to the signal line 30, and the other is connected to the gate of the current control transistor 37. The gate of the driving transistor 36 is connected to the second power supply line 33. The driving transistor 36 and the current control transistor 37 are configured such that the current supplied from the first power supply line 32 is supplied to the light emitting element 39 as the drain current of the driving transistor 36 and the current control transistor 37. The first power line 32 and the light emitting element 39 are connected. In the present embodiment, the source of the current control transistor 37 is connected to the first power supply line 32, and the drain of the drive transistor 36 is connected to the first electrode of the light emitting element 39.

Note that the source of the driving transistor 36 may be connected to the first power supply line 32, and the drain of the current control transistor 37 may be connected to the first electrode of the light emitting element 39.

A potential difference is applied to each of the second electrode and the first power supply line 32 so that a current in the forward bias direction is supplied to the light emitting element 39.

Further, the second electrode is connected to the auxiliary wiring 34 to reduce the substantial resistance value of the second electrode. The auxiliary wiring 34 is preferably formed using a conductive film in the same layer as the signal line 30, the first power supply line 32, and the second power supply line 33, and is the same as the first electrode as shown in FIG. You may form in the layer of.

One of the two electrodes of the capacitor 38 is connected to the first power supply line 32, and the other is connected to the gate of the current control transistor 37. The capacitive element 38 is provided to hold a potential difference between the electrodes of the capacitive element 38 when the switching transistor 35 is in a non-selected state (off state). However, when the gate capacitance of the switching transistor 35, the driving transistor 36, or the current control transistor 37 is large and the leakage current from each transistor is within an allowable range, the capacitor element 38 need not be provided.

In FIG. 1, the driving transistor 36 and the current control transistor 37 are p-channel transistors, and the source of the driving transistor 36 and the anode of the light emitting element 39 are connected. Conversely, when the driving transistor 36 and the current control transistor 37 are n-channel transistors, the source of the driving transistor 36 and the cathode of the light emitting element 39 are connected.

Next, a method for driving the pixel illustrated in FIG. 7A is described by being divided into a writing period and a holding period. First, when the scanning line 31 is selected in the writing period, the switching transistor 35 connected to the scanning line 31 is turned on. Then, the video signal input to the signal line 30 is input to the gate of the current control transistor 37 via the switching transistor 35. Note that the driving transistor 36 is always turned on because the gate is connected to the first power supply line 32.

When the current control transistor 37 is turned on by the video signal, a current is supplied to the light emitting element 39 via the first power line 32. At this time, since the current control transistor 37 operates in the linear region, the current flowing through the light emitting element 39 is determined by the voltage-current characteristics of the driving transistor 36 and the light emitting element 39 operating in the saturation region. The light emitting element 39 emits light with a luminance corresponding to the supplied current.

Further, when the current control transistor 37 is turned off by the video signal, no current is supplied to the light emitting element 39.

In the holding period, the switching transistor 35 is turned off by controlling the potential of the scanning line 31, and the potential of the video signal written in the writing period is held. When the current control transistor 37 is turned on in the writing period, since the potential of the video signal is held by the capacitor 38, supply of current to the light emitting element 39 is maintained. On the other hand, when the current control transistor 37 is turned off in the writing period, since the potential of the video signal is held by the capacitor 38, no current is supplied to the light emitting element 39.

The pixel circuit illustrated in FIG. 7B is different from that in FIG. 7A in that a transistor (erase transistor) 40 for erasing the potential of a written video signal is provided. The gate of the erasing transistor 40 is connected to the second scanning line 41, and one of the source and the drain is connected to the first power supply line 32 and the other is connected to the gate of the current control transistor 37.

The other structure is the same as that in FIG. 7A, and the second electrode of the light-emitting element 39 is connected to the auxiliary wiring 34 so as to reduce the substantial resistance value of the second electrode.

Next, the pixel driving method illustrated in FIG. 7B is described by being divided into an erasing period in addition to a writing period and a holding period.

In the erasing period, the second scanning line 41 is selected, the erasing transistor 40 is turned on, and the potential of the power supply line 32 is applied to the gate of the current control transistor 37 via the erasing transistor 40. Therefore, since the current control transistor 37 is turned off, a state in which no current is forcibly supplied to the light emitting element 39 can be created.

The pixel circuit illustrated in FIG. 7C is different from that in FIG. 7A in that the gate of the driving transistor 36 is connected to the third scanning line 45. The gate line of the driving transistor 36 may be connected to a wiring to which a fixed potential is supplied. The auxiliary wiring 34 is preferably formed using a conductive film in the same layer as the first scanning line 31 and the third scanning line 45.

The other structure is the same as that in FIG. 7A, and the second electrode of the light-emitting element 39 is connected to the auxiliary wiring 34 so as to reduce the substantial resistance value of the second electrode.

A driving method of the pixel illustrated in FIG. 7C is similar to the driving method described with reference to FIG.

The pixel circuit illustrated in FIG. 7D has a structure in which an erasing transistor 40 is provided in the pixel circuit illustrated in FIG. 7C, as in FIG. 7B.

The other structure is the same as that in FIG. 7C, and the second electrode of the light-emitting element 39 is connected to the auxiliary wiring 34 so as to reduce the substantial resistance value of the second electrode.

A driving method of the pixel illustrated in FIG. 7C is similar to the driving method described with reference to FIG.

  The pixel circuit illustrated in FIG. 7E is different from that in FIG. 7B in that the driving transistor 36 whose gate electrode is a fixed potential is not provided and the light-emitting element 39 is controlled by the current control transistor 37. .

In FIG. 7E, the current control transistor 37 is preferably operated in a saturation region so as not to be affected by deterioration of the light emitting element. When operating in the saturation region, it is necessary to consider the voltage of the sum of the voltage drop margin of the second electrode and the deterioration margin of the light emitting element, but the auxiliary wiring reduces the voltage drop of the second electrode. Since the margin can be eliminated, the power consumption of the display device can be reduced.

The other structure is the same as that in FIG. 7B, and the second electrode of the light-emitting element 39 is connected to the auxiliary wiring 34 so as to reduce the substantial resistance value of the second electrode.

A driving method of the pixel illustrated in FIG. 7E is similar to the driving method described with reference to FIG.

Needless to say, as in FIGS. 7A and 7C, the erasing transistor of the pixel circuit in FIG.

7A to 7E, the pixel type in which a voltage signal is input to the signal line 30 as a video signal has been described. However, a pixel type in which a current signal is input as a video signal may be used. However, since the substantial resistance value of the wiring and electrodes can be reduced and the accompanying voltage drop can be prevented, the configuration having the auxiliary wiring has a remarkable effect when applied to a pixel type to which a voltage signal is input. .

Further, although the pixel circuit having a light emitting element has been described, the pixel circuit having a liquid crystal element may have a structure having an auxiliary wiring.

(Embodiment 4)
In this embodiment, an example of a top view of a pixel portion corresponding to the equivalent circuit illustrated in FIG. 7B is described.

FIG. 8 shows a signal line 801, a first power supply line 802, a second scanning line 803, a first scanning line 804, a switching transistor 805, an erasing transistor 806, a driving transistor 807, and a current control transistor 808. , A first electrode 809, an auxiliary wiring 810, a second power supply line 811, and a capacitor 812 are provided.

In this embodiment mode, the signal line 801, the first power supply line 802, and the second power supply line 811 are formed by patterning the same conductive film. Further, a source wiring and a drain wiring of a transistor are formed from the same conductive film. The first scanning line 804 and the second scanning line 803 are formed by patterning the same conductive film. In addition, part of the first scan line 804 and the second scan line 803 overlaps with the semiconductor film and functions as a gate electrode.

The auxiliary wiring 810 is formed over the first power supply line 802 and the second power supply line 811 via an insulating film. Therefore, the auxiliary wiring 810 having a large area can be formed. When a capacitance is generated between the auxiliary wiring, the first power supply line, and the second power supply line, the auxiliary wiring may be used as a capacitor element. Further, unnecessary capacitance can be reduced by using a low-K material for the insulating film. The auxiliary wiring 810 can be formed in the same layer as the first power supply line 802 and the second power supply line 811. In this case, in order to obtain a predetermined resistance value, the film thickness of the auxiliary wiring is determined.

In order to operate the driving transistor 807 in the saturation region, the L / W is designed to be larger than that of the current control transistor 808. For example, L / W of the driving transistor: L / W of the current control transistor = 5 to 6000: 1. Therefore, in this embodiment mode, the semiconductor film of the driving transistor 807 is formed in a rectangular shape.

The capacitor 812 includes a protective film having SiN sandwiched between the second power supply line 811 and the semiconductor film of the driving transistor 807, and a second insulating film.

Next, FIGS. 9A to 9C are cross-sectional views in a state where the auxiliary wiring 810 is formed.

FIG. 9A corresponds to A-A ′ in FIG. 8, and shows a cross-sectional view of the auxiliary wiring 810 formed above the erasing transistor 806 in which the switching transistor 805 and the erasing transistor 806 are formed.

FIG. 9B corresponds to BB ′ in FIG. 8, and the capacitor 812 formed between the driving transistor 807, the second power supply line 811, and the semiconductor film of the driving transistor 807. 9A and 9B are cross-sectional views of a part of a semiconductor film of a current control transistor 808, a first electrode 809, and an auxiliary wiring 810. The driving transistor 807 and the current control transistor may have an LDD (Light doped drain) structure having a low concentration impurity region and a GOLD (Gate-drain Overlapped LDD) structure in which the low concentration impurity region and the gate electrode overlap.

FIG. 9C corresponds to C-C ′ in FIG. 8 and shows a cross-sectional view of the second power supply line 811, the first electrode 809, and the auxiliary wiring 810.

10A to 10C, a third insulating film corresponding to a bank is formed on the auxiliary wiring 810, the light emitting layer 815 is covered in the opening of the third insulating film, and the second electrode is covered. A cross-sectional view in which 816 is formed is shown.

FIGS. 10A and 10C correspond to A-A ′ and C-C ′ in FIG. 8 and are cross-sectional views in the case where a third insulating film is formed over the auxiliary wiring 810. FIG. 10B corresponds to BB ′ in FIG. 8, and a first contact hole and a second contact are formed in the third insulating film over the first electrode 809 and the auxiliary wiring 810, respectively. A cross-sectional view in the case where a hole is formed, a light emitting layer 815 is formed in the first contact hole, the light emitting layer 815 is covered, and a second electrode 816 is formed in the second contact hole is shown.

  The structure shown in FIGS. 8 to 10 corresponds to the structure shown in FIG. 1A, but in this embodiment, the structure shown in FIGS. 1B and 1C can also be used.

By connecting the second electrode 816 and the auxiliary wiring 810 in this manner, a substantial resistance value can be reduced. As a result, power consumption in the display device can be reduced.

  In addition, signal writing failure and gradation failure due to wiring resistance can be prevented. Furthermore, in the case of the second electrode, by connecting to the auxiliary wiring, the occurrence of a voltage drop can be suppressed, and a uniform predetermined voltage can be applied to the light emitting element. As a result, an improvement in display quality can be achieved.

  In particular, in a large display device, the effect of lowering the substantial resistance value of electrodes and wirings is remarkable.

(Embodiment 5)
As a display device and an electronic device of the present invention, a video camera, a digital camera, a goggle type display (head mounted display), a navigation system, a sound reproduction device (car audio, audio component, etc.), a notebook personal computer, a game device, a mobile phone An information terminal (mobile computer, mobile phone, portable game machine, electronic book, etc.), an image playback device equipped with a recording medium (specifically, a recording medium such as a digital versatile disc (DVD) is played back and the image is displayed. And a device equipped with a display that can be used. In particular, it is desirable to use the auxiliary wiring of the present invention for a large television having a large screen. Specific examples of these electronic devices are shown in FIGS.

FIG. 13A illustrates a large display device including a housing 2001, a support base 2002, a display portion 2003, a speaker portion 2004, a video input terminal 2005, and the like. The auxiliary wiring of the present invention can be connected to a wiring or an electrode provided in the display portion 2003 so that a substantial resistance of the wiring or the electrode can be reduced. As a result, in a large display device having a long wiring length, it is possible to reduce voltage drop and signal rounding. The display devices include all information display devices for personal computers, for receiving TV broadcasts, for displaying advertisements, and the like.

FIG. 13B shows a laptop personal computer, which includes a main body 2201, a housing 2202, a display portion 2203, a keyboard 2204, an external connection port 2205, a pointing mouse 2206, and the like. The auxiliary wiring of the present invention can be connected to a wiring or an electrode provided in the display portion 2203 so that a substantial resistance of the wiring or the electrode can be reduced.

FIG. 13C illustrates a portable image reproducing device (specifically, a DVD reproducing device) provided with a recording medium, which includes a main body 2401, a housing 2402, a display portion A2403, a display portion B2404, and a recording medium (DVD or the like). A reading unit 2405, operation keys 2406, a speaker unit 2407, and the like are included. The display portion A 2403 mainly displays image information, and the display portion B 2404 mainly displays character information. The auxiliary wiring of the present invention is connected to the wiring and electrodes provided in the display portions A, B 2403 and 2404, and the wiring and electrodes Can reduce the substantial resistance. Note that an image reproducing device provided with a recording medium includes a home game machine and the like.

  As described above, the applicable range of the present invention is so wide that it can be used for electronic devices in various fields. In addition, any of the structures described in Embodiments 1 to 4 can be used for the electronic device described in this embodiment.

Example 1
In this example, when Al-Si and Al-Ti are used as the material for the auxiliary wiring and the line width of the auxiliary wiring is changed in the range of 2 to 82 μm, the resistance values are 0.01Ω, 0.1Ω, 1Ω, 5Ω. The film thickness required to obtain FIG. 11 shows the result using Al—Si, and FIG. 12 shows the result using Al—Ti.

In addition, using the calculation formula: R = R _real × ( _ds / d) × (W _s / W), an apparent resistance value that can be achieved by changing the width and film thickness of the auxiliary wiring is R, W: actual width of auxiliary wiring, d: actual thickness of auxiliary wiring, W _s : width of auxiliary wiring in design, d _s : film thickness of auxiliary wiring in design, R _real : actual thickness of each material Let resistivity. The actual resistivity of Al—Si and Al—Ti: R _real is 4.1 × 10 ⁻⁶ Ω · cm and 8.5 × 10 ⁻⁶ Ω · cm, respectively.

  The desired resistance value of the auxiliary wiring also depends on the panel size of the display device. Since the wiring becomes longer as the panel size becomes larger, it is desirable that the resistance value of the auxiliary wiring becomes smaller. Here, attention is focused on a resistance value of 0.1Ω. 11 and 12, in order to obtain a resistance value of 0.1Ω, when Al—Si is used, the auxiliary wiring width needs to be about 30 μm and a film thickness of 4000 mm (400 nm). It can be seen that a wiring width of about 60 μm and a film thickness of 4000 mm (400 nm) are necessary.

  Although the width and film thickness of the auxiliary wiring are limited, a film thickness of 4000 mm (400 nm) is a practical value. In the case of a bottom emission type display device, it is not desirable that the width of the auxiliary wiring exceeds the width of the insulating film corresponding to the bank in consideration of the aperture ratio. Therefore, when the width of the auxiliary wiring is required to be greater than the width of the bank, the auxiliary wiring is preferably laminated.

  In the case of a top emission display device, when the auxiliary wiring is formed in a layer different from the anode as shown in FIG. 1B, the width of the auxiliary wiring need not be the bank width. As a result, a lower sheet resistance value can be achieved.

FIG. 6 is a cross-sectional view of a pixel portion of a display device of the present invention. The figure which shows the whole display apparatus of this invention. The figure which shows the auxiliary wiring in the display apparatus of this invention. The figure which shows the auxiliary wiring in the display apparatus of this invention. The figure which shows the auxiliary wiring in the display apparatus of this invention. The figure which shows the auxiliary wiring in the display apparatus of this invention. FIG. 6 illustrates a pixel circuit of a display device of the present invention. FIG. 6 shows a top view of a pixel portion of a display device of the present invention. FIG. 6 is a cross-sectional view of a pixel portion of a display device of the present invention. FIG. 6 is a cross-sectional view of a pixel portion of a display device of the present invention. The figure which shows the experimental result regarding the film thickness and width | variety of the auxiliary wiring of this invention. The figure which shows the experimental result regarding the film thickness and width | variety of the auxiliary wiring of this invention. 4A and 4B illustrate a display device and an electronic device of the invention.

Claims (9)

A first insulating film;
A first electrode provided on the first insulating film;
A second insulating film provided on the first electrode;
A first opening provided in the second insulating film;
A light emitting layer provided on the second insulating film and provided on the first electrode in the first opening;
A second electrode provided on the light emitting layer,
The first insulating film is provided with a second opening,
The second insulating film is provided with a third opening,
Auxiliary wiring is provided at a position in the second opening and in the third opening ,
The light emitting device is characterized in that the light emitting layer is provided on an upper surface of the auxiliary wiring, and the auxiliary wiring and the second electrode are electrically connected on a side surface of the auxiliary wiring. Wiring and
A first insulating film provided on the wiring;
A first opening provided in the first insulating film;
A first electrode provided on the first insulating film and electrically connected to the wiring in the first opening;
A second insulating film provided on the first electrode;
A second opening provided in the second insulating film;
A light emitting layer provided on the second insulating film and provided on the first electrode in the second opening;
A second electrode provided on the light emitting layer,
The first insulating film is provided with a third opening,
The second insulating film is provided with a fourth opening,
Auxiliary wiring is provided in a position in the third opening and in the fourth opening ,
The light emitting device is characterized in that the light emitting layer is provided on an upper surface of the auxiliary wiring, and the auxiliary wiring and the second electrode are electrically connected on a side surface of the auxiliary wiring. 3. The light emitting device according to claim 2, wherein the auxiliary wiring is provided in the same material and in the same layer as the wiring. 2. The light-emitting device according to claim 1, wherein the third opening has a diameter such that the side surface of the auxiliary wiring does not come into contact with an end of the second insulating film. 3. The third opening according to claim 2, wherein the third opening has a diameter such that the side surface of the auxiliary wiring is not in contact with an end of the first insulating film, and the fourth opening is the auxiliary wiring. The side surface of the light emitting device has a diameter that does not contact the end of the second insulating film. Form wiring and auxiliary wiring,
Forming a first insulating film on the wiring and the auxiliary wiring;
Forming a first opening and a second opening in the first insulating film, exposing the wiring from the first opening, and exposing the auxiliary wiring from the second opening; ,
Forming a first electrode electrically connected to the wiring in the first opening;
Forming a second insulating film on the first insulating film, the first electrode, and the auxiliary wiring;
A third opening and a fourth opening are formed in the second insulating film, the first electrode is exposed from the third opening, and the auxiliary wiring is formed from the fourth opening. To expose
Forming a light emitting layer on the second insulating film, the first electrode, and the auxiliary wiring;
A method for manufacturing a light-emitting device in which a second electrode is formed on the light-emitting layer,
The light emitting layer is formed on an upper surface of the auxiliary wiring, and a side surface of the auxiliary wiring is electrically connected to the second electrode. Form wiring and auxiliary wiring,
A solution containing an organic material is applied to the wiring and the auxiliary wiring, the organic material is heated and baked, and the baked organic material is exposed to form a first opening and a second opening. Forming the first insulating film having the following: exposing the wiring from the first opening, and exposing the auxiliary wiring from the second opening;
Forming a first electrode electrically connected to the wiring in the first opening;
Forming a second insulating film on the first insulating film, the first electrode, and the auxiliary wiring;
A third opening and a fourth opening are formed in the second insulating film, the first electrode is exposed from the third opening, and the auxiliary wiring is formed from the fourth opening. To expose
Forming a light emitting layer on the second insulating film, the first electrode, and the auxiliary wiring;
A method for manufacturing a light-emitting device in which a second electrode is formed on the light-emitting layer,
The light emitting layer is formed on an upper surface of the auxiliary wiring, and a side surface of the auxiliary wiring is electrically connected to the second electrode. In Claim 6 or Claim 7 , the second opening has a diameter such that the side surface of the auxiliary wiring does not contact the end of the first insulating film, and the fourth opening is A method for manufacturing a light-emitting device, wherein the side surface of the auxiliary wiring has a diameter that does not contact an end portion of the second insulating film. In any one of claims 6 to 8, the auxiliary line, a method for manufacturing a light-emitting device characterized by being formed simultaneously with the wiring.

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